Voltage suppression network for ignition systems



Aug. 2, 1966 e. o. HUNTZINGER ETAL 3, 1

VOLTAGE SUPPRESSION NETWORK FOR IGNITION SYSTEMS Filed Dec. 6, 1962 INVENTORS GERALD O. HUNTZINGEB WILLIAM D, WORRELL BY (LRWM TH E IR ATTORNEY United States Patent 3,264,521 VOLTAGE SUPPRESSKOJN NETWORK FOR IGNITION SYSTEMS Gerald O. Huntzinger and Wiliiam D. Worrell i, Anderson,

Ind., assignors to General Motors Corporation, Detroit,

Mich, a corporation of Delaware Filed Dec. 6, 1962, Ser. No. 242,687 3 Claims. ((11. 315-224) This invention relates to ignition systems for internal combustion engines and more particularly to an ignition system that is provided with a voltage suppression network for reducing the voltage induced in the ignition coil of the system when the primary winding of the ignition coil is being supplied with current.

In ignition systems wherein an ignition coil is used, the current flow to the primary winding of the ignition coil is periodically interrupted so that a high voltage is induced in the secondary winding which is then applied to a spark plug of the internal combustion engine. The interrupting function for the primary current in the past has been accomplished by breaker points which are opened and closed in synchronism with operation of the engine. More recently, semiconductors have been used to open and close the primary circuit and the turning on and off of the semiconductors has been controlled in synchronism with the engine.

In some types of ignition systems that use semiconductors, the turning on of the current for the primary winding occurs, for example, at only 5 before the turning oif of this current and this turning off occurs when a rotor segment of a distributor is aligned with an insert in the distributor cap. This means that the rotor segment is quite close to a distributor cap insert when the primary circuit is made as compared to angles which have previously been used in conventional ignition systems where the angle that is traversed by a breaker cam may be 30 between the turning on of the primary current and the subsequent turning off of the primary current when the breaker contacts open. A problem encountered with the smaller angle is the problem of a possible misfiring between the rotating rotor segment of the distributor and one of the electrodes or inserts carried by the distributor cap during the time that the primary circuit is initially being made or completed. Thus, the rotor segment or contact may be close enough to one of the inserts in the distributor cap that the gap at times can be fired when the primary circuit is being made rather than when it is being broken. This, of course, causes a misfiring of the engine which is highly detrimental.

It accordingly is one of the objects of this invention to provide an ignition system which has a voltage suppression network for reducing the voltage induced in the ignition coil when the circuit is being made to the primary winding of the ignition coil.

Another object of this invention is to provide an ignition system wherein the primary winding of the ignition coil is connected in parallel with a voltage suppression network which includes a capacitor, a resistor and a diode.

Still another object of this invention is to provide a breakerless semiconductor ignition system which has a voltage suppression network for reducing the voltage induced in the ignition coil when the circuit is made to the primary winding.

A further object of this invention is to provide an ignition system which is controlled by a magnetic pick-up and which has a voltage suppression network for reducing the voltage induced in the ignition coil when the circuit is made to the primary winding of the ignition coil by a semiconductor switch means which may be a transistor.

Further objects and advantages of the present invention will be apparent from the following description, reference 3,Zh,52i Patented August 2, 1966 "ice being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings, the single figure drawing is a schematic circuit diagram of an ignition system which has the voltage suppression network of this invention.

Referring now to the drawing, the reference numeral 10 designates a conventional internal combustion engine the combustible mixture of which is fired by the spark plugs 12. The engine in this case is an eight cylinder engine with eight spark plugs for firing the combustible mixture of the cylinders in a predetermined sequence as is well known to those skilled in the art.

The spark plugs 12 are connected with the inserts or metal electrodes 14 of an electrical distributing device which is generally designated by reference numeral 16. This electrical distributing device may be a conventional distributor cap having the electrodes 14 connected respectively with the spark plugs 12. A rotor contact 18 which is driven by the engine 10 swings in close proximity to the inserts or electrodes 14 to distribute spark impulses to the spark plugs 12 from a high voltage conductor 20. This distributor cap and the rotor contact 18 may be of the type shown in copending application, Serial No. 126,406, filed on June 16, 1961, and assigned to the as signee of this invention.

The high voltage conductor 20 is connected to one side of the secondary winding 22 of an ignition coil 24. The ignition coil 24 has a primary winding 26 one side of which is connected with a grounded power conductor 28. It is seen that one side of the secondary winding 22 is also connected with the grounded power conductor 28. It will, of course, be appreciated that the various circuit elements that are connected with conductor 28 can be directly grounded on a motor vehicle electrical system. It is also seen that the power conductor 28 is connected with the negative side of a DC. voltage source designated by reference numeral 34! which is shown as a battery. The battery 30 will, of course, be supplied with charging current from a generator in a motor vehicle electrical sys tem and the voltage that is supplied to the ignition system of this invention may come from the generator when the engine is operating.

The current flow for the primary winding 26 of ignition coil 24 is controlled by a three terminal semiconductor switch means which in the embodiment illustrated takes the form of a PNP transistor 32 which has its collector electrode connected with junction 34 and thus to one side of the primary winding 26. The emitter electrode of transistor 32 is connected with junction 36 which is connected with a conductor 38. A resistor 48 connects the conductor 38 with a power conductor 42 which is connected to one side of the ignition switch 44. The opposite side of the ignition switch is connected with the positive side of the DC. source 30 via a conductor 46.

The base electrode of transistor 32 is connected with a junction 48 and to one side of the secondary winding 50 of a coupling transformer 52. The opposite side of the secondary winding 50 is connected with junction 36 and it therefore is seen that the secondary winding Si) is connected across the emitter and base electrodes of transistor 32. The primary winding 54 of the coupling transformer 52 is connected between the collector electrode of a PNP transistor 56 and the conductor 58. The conductor 58 is connected to one side of a feedback coil 69 which is wound on a magnetic core 62. The opposite side of the feedback coil 60 is connected with the power conductor 28 at junction 64.

The emitter electrode of transistor 56 is connected with the power conductor 42 while the base electrode of transistor 56 is connected with junction 66 on conductor 68.

The ignition system of this invention is controlled by a voltage generating device which is generally designated by reference numeral 70. .This pulse generating device includes the magnetic core 62 having pole faces 62a and 621) which are positioned on opposite sides of a rotor 72 that is formed of magnetic material. has eight radially extending teeth or pole tips which become progressively aligned with the pole faces 62a and 62b as the rotor 72 rotates. The rotor 72 is driven in synchronism with the engine and its speed of rotation is therefore a function of engine speed. .A fiow of magnetic flux is forced through the magnetic core 62 and between pole faces 62a and 62b and through the rotor 72 by a permanent magnet '74. It will, of course, be appreciated that an electrical coil could be substituted for thepermanent magnet to provide the flow of flux The rotor 72 through the magnetic core 62. In such an arrangement,

the electrical coil would have to be supplied ith current.

A pick-up coil 76is wound on the magnetic core62 and an A.C. voltage is induced in this pick-up coilas the rotor 72 rotates. As a pairof projecting teeth of the rotor 72 are swinging into alignment with pole faces 62a and 62b, a voltage pulse of one polarity is induced in the pick-up coil 76. As the same rotor teeth'now swing out of alignment with the pole faces 62a and 625, a voltage pulse of an opposite polarity is induced in the pick-up coil 75. eight alternating voltage pulses are induced in the pickup coil 76 for every revolution of the rotor 72.

One side of the pick-up coil 76 is connected with conductor 68 and is therefore connected with the base electrode of transistor 56. The opposite side of. the pick-up coil 76 is connected with junction 78. A capacitor 80 connects the junction 78 with the power conductor 42. A diode 82 is connected between junctions 78 and 34; Another diode 86 connects the junction 84 with the power conductor 42. A capacitor90 is connected between. junctions 84 and 48. A resistor Q2 connects the junction 66 with the junction 94 on conductor 38.

The voltage suppression network of this invention is connected across theprimary winding 26 and is therefore connected across junctions 34 and 96. This voltage suppression network includes a diode 98 connectedwith junction 34 and a capacitor 100 connected between conductors 102 and 104. A resistor 106 is connected in parallel with the capacitor 109.

When the engine is being cranked or when the engine is operating, the rotor 72 rotates and an AC. voltage is induced in the pick-up coil 76. At one point inthe cycle of this AC. voltage, the base electrode of transistor 56is negative with respect to the emitter electrode.

It will of course be appreciated that- This turns on the transistor 56 in its emitter-collector circuit and a current flows from conductor 42, through the emitter-collector circuit of transistor 56, through the primary Winding 54 of coupling transformer 52, through feedback winding 60 and then to junction 64. When current flows through the feedback winding 60, a voltage is induced in the pick-up coil 76 which turnson the transistor 56 to a greater extent. In addition, when coupling transformer 52, a voltage is induced in the secondary winding 50 which is of such a polarity as to drive the emitter of transistor 32 positive with respect to its base. This will turn on the transistor 32 in its emitter-collector circuit.

current'fiows through the primary winding 54 of the.

When transistor 32 turns on in its emitter-collector circuit, current can flow from power conductort42, through resistor 40, through conductor 38,through the emitter-collector circuit of transistor 32, and through the primary winding 26 of the ignition transformer to junction 96. Current can also flow from the junction 34, through diode 98, and through the capacitor 100 which at this time represents a very low impedance to the initial buildup of current o that a large portion v 4 of the initial surge of current will pass through the capacitor 100. This causes the initial rateofbuild-up V of-current through the primary winding 26 of the ignition coil to betrnuch lower than it would be if the network consisting of diode 98; capacitor 1160." and resistor 196 was not present. A voltagewill-be inducedin' theignition coil 24 which is. proportional to. the rate .of build-up of current through the primary winding .22, but since the initial rate of build-up of current through the primary winding is reduced, the initial voltage induced in the ignition coil will be reduced.

As the flow of currentxthrough the primary. winding of the ignition coil 24 approaches itssteady state value,

the voltage induced in the ignition coil 24 will reduce until the potential at junction 34 becomes less positive than the voltage at junctiontltlsr When this happens, current will cease to flow-through the diode gSand into-the capacinow induced in secondary winding Stlwhich is of such-a.

polarity as to turnoff the transistor 32. When this happens, the current flow for the primary winding 26 :is interrupted and a high voltage isiinduced in thexsecon-dary winding 22 which isapplied to one of the spark plugs 12, through the conductor 2ti,"rotor contact 18,. distributor cap electrode l t-"and the conductor connecting this electrode with one of=the spark plugs 12. The capacitoruitlis used to providea potential-which delays the turning on of the. transistor 56 and thus insures that the on time. of transistors 56' and 32 is substantially constant over the widely varying speedrange of the engine 10. This capacitor can be charged from the pick-up coil 76":and can also be charged from the secondary :winding 50 of the coupling,.,transformer through the capacitor 90 and the diode 82. The capacitor 90 is charged through diode 86 from the secondary winding 50 whenever the -voltage. output: of the secondary .winding 50 is of such a polarity that the junction 36 4s positive with respect to. junction 48. The amount of charge thus accumulatedon the capacitor 90 is a function of the time that the junction 36 :is positive withrespect to the junction 48. During these time intervals the transistor'32 is biased to conduct.

winding 26.

The voltagesuppression network of'this invention can be used with ignition systems other than the type shown in the drawing and will beuseful in anyignition system Where it is desired to reduce the :voltageinduced in the ignition coil when the circuit to the primary winding 26 is initially made.

While thevembodiment of the present-invention as herein disclosed constitutes a preferred form, his toybe understood that other forms'might be adopted.

What is claimed is as follows:

1. Anignition system comprising, an ignition coil having a primary winding and a seconda'ry,a source of direct current,-switch1means connected" in series with'said sourcedof. direct current and in series with'the primarywinding of said. ignition coil, said switch means being adapted to be turned on and off in timed relationship with operation .of' an engine, a diode, means connecting one side of said diode with one side of said primary winding, a capacitor connected. betweenan opposite 'sideof said diode and an opposite side-of said primary winding, and a resistor connected across said capacitor, said capacitor being charged through said diodefrorn said source ofdirect,

AZener diode .lltiis connected across the emitter and collector electrodes of transistor 32..in:orde.r to protect. this transistor frominduced voltages; within the primary current when said switch means is initially closed to reduce the buildup of current in said primary winding, said resistor forming a discharging circuit for said capacitor.

2. An ignition system for an internal combustion en gine comprising, an ignition coil having a primary winding and a secondary winding, said secondary winding being adapted to be connected with a spark plug for said engine, a source of direct current, circuit control means for making and breaking a circuit connected between said source of direct current and the primary winding of said ignition coil in timed relationship with operation of said engine, and means connected with said primary winding for reducing the initial build-up of current in said primary winding when said circuit control means initially closes said circuit between said primary winding and said source of direct current, said means for reducing initial build-up of current in said primary winding including a parallel connected resistor and capacitor which is connected with the primary winding of the ignition coil through a diode, said capacitor being charged from said source of direct current through said diode when the circuit for the primary winding is initially closed.

3. An ignition system for an internal combustion engine comprising, an ignition coil having a primary winding and a secondary winding, said secondary winding being adapted to be connected with a spark plug for said engine, a source of direct current, semiconductor switch means connected between said source of direct current and said primary winding for controlling the current flow through said primary winding, control means driven in synchronism with said engine for controlling the conduction of said semiconductor switch means in timed relationship with operation of said engine, and means connected with said primary winding for reducing the initial build-up of current in said primary winding when said semiconductor switch means initially closes said circuit between said source of direct current and said primary winding, said means for reducing initial build-up of current in said primary winding including a diode connected in series with a parallel-connected resistor and capacitor.

References Cited by the Examiner UNITED STATES PATENTS 2,543,428 2/1951 Wendt et al. 328-67 X 2,602,149 7/1952 Brunelle, et al. 315-223 X 2,651,005 9/ 1953 Tognola 315206 2,850,648 9/1958 Elliott 30788.5 3,007,082 10/1961 Kappele 315-214 3,047,728 7/1962 Martin 315-209 3,131,327 4/1964 Quinn 315223 X 3,152,281 10/ 1964 Robbins 315209 DAVID J. GALVIN, Primary Examiner.

GEORGE N. WESTBY, Examiner. D. E. SRAGOW, R. SEGAL, Assistant Examiners, 

1. AN IGNITION SYSTEM COMPRISING, AN IGNITION COIL HAVING A PRIMARY WINDING AND A SECONDARY, A SOURCE OF DIRECT CURRENT, SWITCH MEANS CONNECTED IN SERIES WITH SAID SOURCE OF DIRECT CURRENT AND IN SERIES WITH THE PRIMARY WINDING OF SAID IGNITION COIL, SAID SWITCH MEANS BEING ADAPTED TO BE TURNED ON AND OFF IN TIMED RELATIONSHIP WITH OPERATION OF AN ENGINE, A DIODE, MEANS CONNECTING ONE SIDE OF SAID DIODE WITH ONE SIDE OF SAID PRIMARY WINDING, A CAPACITOR CONNECGED BETWEEN AN OPPOSITE SIDE OF SAID DIODE AND AN OPPOSITE SIDE OF SAID PRIMARY WINDING, AND A RESISTOR CONNECTED ACROSS SAID CAPACITOR, SAID CAPACITOR BEING CHARGED THROUGH SAID DIODE FROM SAID SOURCE OF DIRECT CURRENT WHEN SAID SWITCH MEANS IS INITIALLY CLOSED TO REDUCE THE BUILDUP OF CURRENT IN SAID PRIMARY WINDING, SAID RESISTOR FORMING A DISCHARGING CIRCUIT FOR SAID CAPACITOR. 